Protective apparatus for combustion systems



Nov. 28, 1950 w. J. WILLENBORG PROTECTIVE APPARATUS FOR CQMBUSTION SYSTEMS Filed Feb. 9, 1946 2 Sheets-$heet 1 l I I l I in V GAS ANALYZER Nov. 28, 1950 w. J. WILLENBORG 2,532,214

PROTECTIVE APPARATUS FOR COMBUSTION SYSTEMS Filed Feb. 9, 1946 2 Sheefs-Shet 2 summon/5m? &%

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IN VEN TOR. ww wy Patentecl Nov. 28, 1950 PROTECTIVE APPARATUS FOR COMBUSTION SYSTEMS Walter J. Willenborg, Weehawken, N. J., assignor to Jabez Burns & Sons, Inc., New York, N. Y., a corporation of New York Application February 9, 1946, Serial No. 646,511

7 Claims.

This invention relates to protective and indicating apparatus for various types of combustion systems such as roasters for coffee and the like. bake ovens and other combustion systems where it is possible for gases and vapors to accumulate in the combustion chamber and in other parts of the system which may create a dangerous condition. The invention also relates to the method of obtaining continous samples of the gases from different parts of the systems during operating and shut down conditions, to the determining.

of the condition of the gases and to the indication and control of parts for protective purposes and for the efiicient operation of the systems.

One object of the invention is to automatically cut oil the fuel supply upon the approach to a dangerous condition and thereby prevent the possibility of an explosion by continued operation. Another object is to indicate to the operator the condition of the gases in the combustion chamber so that he may know whether he is ob taining the most efficient combustion during operation and the extent of any departure therefrom. If incorrect he may then adjust the mixture of air and fuel to proper proportions. A further object is to show the condition of the ,gases in the system during shut down so that if an undesirable or dangerous condition exists, the system may be purged before starting up. Another object is to provide continuous indications to the operator of the condition of the gases in the various parts of the system not only during operation but also during shut down. These and other objects and advantages will be understood from the following description and accompanying drawings which show a preferred embodiment as applied to a roasting machine supplied with illuminating gas as the fuel.

Fig. 1 is a schematic showing of a coffee roaster of known form in which the products of combustion are recirculated and to which this improvement is applied; and Fig. 2 is a diagram showing the electric controlling and responsive devices.

Referring to Fig. l, a perforated roasting cylinder I is indicated within an enclosing casing 2. The cylinder is rotated by an electric motor 3 shown outside the casing. An intake for the gases of combustion to the roasting casing or chamber is shown as a muflle 4 in which the burner is located. The supply of the fuel, illuminating gas in this instance; is from a supply pipe 5 having a main control valve 6 and a shut oii valve I, to an air mixer 8. This air mixer is provided with a power driven fan. The mixed air and gases pass to a burner nozzle 9 extending within the combustion chamber or mufiie 4. A pilot light I0 is shown near the entrance to the combustion chamber and is supplied by a pipe connection, having a shut off valve II, from the main supply pipe 5 at a point between the valves 6 and 1. A runner light l2 extends from near the pilot light to near the burner nozzle and is provided with a stop valve iii in its connection to the pilot light connection. An outlet pipe M extends from the roasting chamber to a power driven fan l5 and the outlet from the fan is connected by a pipe Hi to the combustion chamber for recirculating a portion of the products of combustion through the system. A damper lBa is in the pipe l6. A vent pipe H to atmosphere from the pipe l6 permits the escape of excess gases.

During normal operation such a system is free from danger owing to the low content of oxygen in the heated gases which is insufficient to support combustion. However, unburnt gases may accumulate in the system from various abnormal conditions during operation or during shut down and if the oxygen content should then rise by admission of external air or otherwise, an unsafe explosive mixture may result.

By the present invention samples of the gases from various parts of the apparatus are transmitted to an analyzer which responds to changes in the condition of the gases for indication of their condition and for afiecting controlling means to anticipate and avoid any danger when a dangerous condition is being approached.

In Fig. 1 the analyzer I8 is generally indicated and is later explained. From its right-hand end a pipe connection [9 extends to an open end near the pilot light In at location A and also to an open end at the intake of the mixer 8 at loca tion C. From its left-hand end a pipe connection 20 extends to an open end within the combustion chamber or muflle 4 at location D. A pipe connection 2| also extends from the lefthand end of .the analyzer to the lower side of the recirculating pipe "5 near the exhaust from the recirculating fan |5 at location B. A portion of the pipe 2| contains a means 22, such as a pipe with a series of outwardly extending ribs or flanges, for cooling the gases to reduce the moisture content before passing into the analyzer. The pipe 2| has a downward extension entering a receptacle 23 for receiving the excess moisture. This receptacle has an overflow outlet, the end of the pipe 2| extending within the liquid in the receptacle to form a seal. These pipe connec- 3 tions serve to conduct samples of the gases from the various locations through the analyzer, passing in one direction or the other therethrough according to whether the system is in operation or idle.

Under operating conditions, the flow of gases is from the sampling location B through the analyzer from left to right subjecting it to the condition of the exhaust gases. This flow is due to a suction or minus pressure at the location C due to the suction of the mixer fan drawing the gases through the cell or analyzer from the location B. Also there is a positive pressure at the location B which aids this flow.

If the main gas valves 6 and l, or either of them, be closed, the sample gas will follow the path just described; and in case of a leak of fuel gas through the main valve or valves, the analyzer will respond to any approach to a dangerous condition caused by such a leak.

If, in addition, the damper [6a in the recirculating pipe be closed for venting to atmosphere when water is added to cool the roasted material, the gas sample will continue to be supplied from the location B in the same path and the analyzer will respond to the condition of the exhaust gases.

In case the circulating fan i should stop, the sample will be drawn from both locations B and D by the suction of the mixer fan at 8; and if the fuel gas supply had not been fully shut oil, any leak of gas would be picked up from either or both locations B and D and revealed by the analyzer.

If the circulating fan l5 should stop while the burner 9 is active, the sample would be drawn from location D. The normal conditions would then lack the advantage of recirculation and the fuel would burn rich and produce unburnt products which would affect the response of the analyzer.

If the mixer fan at 8 should stop while other operating conditions continued, the positive pressure due to the fan l5 would cause a flow of sample gas from the location B through the cell I8 to locations A and C and also cause a portion of the gas to pass from B to D. The analyzer or cell l8 would, of course, then reveal too rich a mixture due to the unburnt gases. In some cases the location B and the pipe therefrom may be omitted. In that case when the mixer fan stops, the negative pressure at location D will cause a flow of gas from locations A and C to and through the analyzer ill from right to left and to location D. The analyzer would then respond to reveal too rich 2. mixture.

In shutting down for the idle condition, the pilot gas valves II and I3 are closed as well as the main fuel valve I and then the mixer fan and recirculating fan are stopped. Under this idle condition, the gas sample passes through the analyzer from right to left. This is due to the minus pressure at B and D being greater than the minus pressure at C or A and thereby causing sample gas to pass from locations A and C through the analyzer from right to left. Any leak through the pilot or main fuel supply valves would then be revealed by the analyzer. Also if either the pilot or main burner valves had been left open when both fans were stopped, and whether or not the pilot and main burner continued to burn, the analyzer would show this undesirable condition.

It may be stated generally that the analyzer or cell I8 will respond to any abnormal condition as the circulating fan stopping during the roasting process, the mixer fan stopping while the burner is out or while burning, the pilot light or main burner extinguished during the roasting, the pilot valves or main valve leaking during shut down and various other undesirable conditions.

The present improvement requires that the operator properly start up and shut down the system in proper manner and avoids all leaks, as otherwise the analyzer will respond to cause an indication of the approach to a dangerous condition, or to shut off the fuel supply, or to give a signal or an alarm, or a combination of two or more of such responses. The proper sequence in starting is to first start the mixer and circulating fans which purge the system. The operator may then. after the automatic control valve 6 has been opened, light the pilot and runner lights and then open the main burner valve for starting the burner flame. In shutting down, the main burner and pilot valves should be closed first and then the two fans stopped.

The indicating and control apparatus which is affected by the variable condition of the analyzer or cell I8 is shown diagrammatically in Fig. 2 where the analyzer is shown at the lower left-hand portion. This is shown as a metal block having a through passage at its lower portion to the opposite ends of which are connected the sampling pipes as shown in Fig. 1. In the the upper portion of the block are cylindrical cavities for the reception of cells of the character described in the U. S. Patent No. 2,255,551 of W. J. Willenborg, granted September 9, 1941. There are four such cells indicated inserted in the cylindrical openings of the block IS in Fig. 2 of the present case designated as E, F, G and 1-1. These cells are sealed against atmosphere by sealing washers 24 and support electrical resistors 25 preferably of platinum or tungsten, or other suitable metal, the resistance of which varies with their change in temperature. The resistance of the resistors oi. the cells E and G is preferably made higher than that oi the resistors in cells F and H, this being determined by their length, cross-section or their material.

The openings in which the cells F and G are 10-,

, remain subjected to the composition of the sealed atmosphere.

Any changes in temperature of the analyzer or block as a whole, due to change in ambient temperature or to the temperature of the gases pass-.

ing through the block will uniformly affect the temperature of all the resistors and any resulting relative change in their resistance will not appreciably affect their response.

However, when the composition of the gases passing through the analyzer changes, the resistors in the cells. F and G will be afiected in response to the thermal conductivity of the gases. Thus if the gases" are of a composition having higher conductivity than normal safe conditions, the resistance of the resistors in cells F and G will be reduced because their temperatures will be lowered by the increased dissipation of heat to the passing gases of higher thermal conductivity, the resistors having a positive temperature coeillclent of resistance. This changes the resistance of the resistors in the cells F and G with reference to that of the unaffected resistors in the cells E and H. This relative change is utilized for giving indications thereof and for producing controlling eflects when the change approaches a dangerous condition. It follows that any mixture of gases which has a higher thermal conductivity than that of the proper normal mixture may be detected by this means and continuously reveal the condition of the gases under all operating and idle conditions.

It has been found that in combustion systems of the type to which this invention is applicable, the unburnt gases have a higher thermal conductivity than the most desirable mixture of the gases of combustion, such unburnt gases being for example the flammable gases such as hydrogen, methane and the like. These unburnt gases may accumulate by having too rich or too lean a fuel mixture, or by raw fuel gas entering the system. Normally the oxygen content of the heated gases in the system is small and the mixture is inert and prevents the ignition of flammable gases which may be present in the heated gases; but if this oxygen content be increased as by opening a door to the system or by any opening permitting air to enter the interior, the resulting explosive mixture might be dangerous in the presence of a flame or spark, or a sufiiciently high temperature.

In Fig. 2 the leads from the four resistors are carried out through the cells and are connected in a Wheatstone bridge arrangement. An alternating current source 44 is adapted to be connected by a switch 26 to a transformer and rectifier unit indicated at 21. The direct current leads therefrom are connected respectively to adjustable contacts 26 and 28a which engage variable resistors and 29a for securing proper balancing of the circuits. One side of the bridge connection is from the contact 28 through a portion of the resistor 29, through the resistor in the cell E, then through the resistor in the cell F and thence through a portion of the resistor 29a to the other side of the line at contact 28a. The other side of the bridge circuit is from the contact 28, through a portion of the resistor 29, then through the resistor in the cell G, then the resistor in the cell H and thence through a portion of resistor 29a to the contact 28a. A galvanometer 30 is connected across the bridge from a point between E and F to a point between G and H. The galvanometer has a mid-scale zero point and any change of resistance in the resistors of F and G with reference to that of the resistors E and H will cause a deflection of the indicating needle to the right or left of the zero point. The scale plate may be divided into sections to indicate normal operating conditions in the righthand portion, and caution and danger conditions in the left-hand portion. An additional galvanometer 3! of the contacting type is connected in parallel with the galvanometer 30 and similarly responds to changes in the composition of the gases. The movable vane 31a when sufllciently deflected to the left engages a fixed contact 31b and when deflected to the right engages the fixed contact 3lc. These fixed contacts may be adjustable toward and from the vane for determining the critical conditions for the engagement of the contacts by the vane.

A pair of movable contacts 32 and 33 are simultaneously controlled by an electromagnet having a winding 34 connected from one terminal through a resistor 35 to one side 36 of the supply line. The other terminal is connected to a fixed contact 32a adapted to be engaged by the contact 32 and also to the vane 3m and to one side of a starting push button 31. The other side of the push button is connected to the supply line 38. The fixed contacts 3!!) and 3lc are both connected to the connection between the magnet winding 34 and the resistor 36. The movable contact 32 is connected to the supply line 38. Another electromagnet having a winding 33 has one terminal of the winding connected to the supply line 38 and its other terminal connected to the fixed contact 33a adapted to be engaged by the movable contact 33 when the winding 34 is energized. The contact 33 is connected to the supply line 36. An indicating lamp 43 which may have a green bulb is connected across the terminals of the magnet winding 39 showing when it is energized under normal operating conditions. An indicating lamp 4| which may have a red bulb and an alarm bell or other form of signal 42 are connected in parallel from the line 38 to the fixed contact 33b adapted to be engaged by the contact 33 when the magnet winding 34 is deenergized. The valve 6 already referred to in describing Fig. 1 as being in the main fuel supply pipe 5, is adapted to be held in its open position when the controlling winding 39 is energized and to be automatically closed when the winding is deenergized. A pivoted hand lever 43 is provided for manually moving the valve 6 to its open position where it is then held provided the winding 39 be energized.

Fig. 2 shows the parts in their complete shut down condition. In starting up, the recirculating fan l5 of the system should first be started to purge the system of any accumulated gases and the mixer fan 8 should also be started. The switch 26 is then closed which supplies current to the bridge circuit through the transformer and rectifier 21. The pointer of the galvanometer 30 and the vane of the galvanometer 3| will then occupy their mid-positions, the contacts 28 and 2821 having been adjusted for this condition. The push button 31 will then be closed temporarily which causes the winding 34 to be energized by a circuit from line 38 through the button, winding 34 and resistor 35 to line 36. This causes the movable contacts 32 and 33 to engage their contacts 32a and 33a. The winding 34 is then maintained energized by a circuit from line 38 through contacts 32, 32a, winding 34, resistor 35 to line 36. The engagement of the contacts 33 and 33a closes a circuit through the winding 39 and the green light 40 across the lines 36 and 38. The control valve 6 may now be opened manually and will be held, open by the magnet if conditions remain normal. The pilot and runner valves H and I3 of Fig. 1 when now opened permit the pilot and runner lights to be ignited. The fuel valve 1 may now be opened which places the system in operation for starting the roast,

Under normal operating conditions, the needle and vane of the instruments 30 and 3| move somewhat to the right of their mid-positions because the heated gases then have a lower thermal conductivity than the air previously in the system as is determined by the sample gases passed through the analyzer. The scale of the galvanometer 30 maybe marked to indicate thisnormal desirable condition.

If the fuel gas mixture becomes leaner or richer it will be indicated by m ve of the pointer from its normal position and the operator may then make adjustments of the fuel or air supply or both accordingly. These indications of.the galvanometer are, of course, due to the change of resistance of the resistors in the cells F and G relatively to the resistance of the resistors in the cells E and H caused by the change in thermal conductivity of the sample gases. The result is to modify the relative drop in volts in the resistors of the bridge circuit, giving a corresponding indication by the galvanom eter in the usual function of a Wheatst'one bridge.

In case the presence of flammable gases becomesunduly high due to any of the causes already referred to, such as an extinguished pilot light, the needle will swing to the left of the midscale position into a region which may be marked caution. This gives a warning to the operator to correct the trouble. However, if the condition be notremedied and the accumulation of flammable gases be allowed to continue sufliciently, the needle will move further to the left to a region which may be marked danger. The vane 3la of the other galvanometer has the same movement as the needle, moving to the left as a dangerous condition is approached. The fixed contact 3") is so positioned that it will be engaged by the vane 3Ia at a condition well below the attaining of a condition when an explosion might result, giving an ample factor of safety. Such contact engagement will short-circuit the magnet winding 34 by a. circuit from the upper terminal of the winding through SI!) and 3Ia to the lower terminal of the winding. This magnet is then deenergized causing an opening at contacts 32a and 33a and a, closing at contact 33b.

The holding circuit of the winding 34 is thereby opened as well as the circuit of winding 39. The control valve 6 is then automatically closed shutting 'off all fuel supply. The operator must then close the fuel valve 1 and pilot valves II and I3, purge the system and restart in the manner described after remedying the trouble. When the winding 39 is automatically deenergized, the contact 33 engages the contact 33b which closes the alarm and red light circuit across the supply lines giving a signal to the operator of the automatic shut-off. It will be understood that under any of the abnormal conditions previously described arising during operation, the analyzer will respond to affect the bridge circuit, the instruments and the automatic control apparatus according to the composition of the gases in the different parts of the system.

Also when the system is idle, as between roasts or over longer periods, and the magnet windings 34 and 39 remain energized, which is the normal non-operating condition, the analyzer will reveal the condition of the gases to the instruments and cause the controls to function in the manner just described, it having been explained in connection with Fig. 1 how the sample gases are passed through the analyzer during idle conditions as well as during operating conditions. Thus any of the abnormal conditions which may occur, such as the various examples already explained, will be revealed by the control apparatus and result in its automatic action if a dangerous condition is sufliciently approached.

A further protection is secured by the automatic control of the valve 6 in case of failure of any of the resistors in any one of the cells. The contact lie of the instrument 3| is connected with the contact Ilb. If any one resistor fails, as by opening its circuit, the vane 31a will move fully to the right or left depending on which resistor is faulty. This will short-circuit the winding II and cause th automatic closing of the valve 8, as already explained. The defective cell must then be re-. placed for restoring the normal" functioning of the control.

Although a particular embodiment of the invention has been shown and described as applied to one form of combustion apparatus using illuminating gas as the fuel in a roaster, it will be understood that the invention is applicable to other combustion systems and to the use of other fuels. In some cases where the character of the apparatus does not produce sufllcient difference in pressures to pass the sample gases through the analyzer under the various conditions which may arise, special means may be added to the apparatus for producing the pressure differences. Also various modifications of the invention may be made for adaptation to particular requirements without departing from the scope of the claims.

I claim:

l. The combination of combustion apparatus having a gaseous fuel supply including a supply pipe, conduit means for withdrawing gases from said apparatus, an analyzer in said conduit means having a resistor responsive to the amount of flammable gases present in the composition of the gases withdrawn from the apparatus by the change of its resistance upon the lowering of its temperature by the presence of such flammable gases, a bridge circuit wherein said resistor is connected in one of the legs of the bridge circuit, a shut-off valve in the supply pipe of the fuel supply, a contact device electrically connected to said bridge circuit and actuated to its closed position when the presence of the flammable gases in said apparatus approaches a dangerous condition, and electromagnetic means affected by the closing of said contact device for closing said valve.

2. The combination of combustion apparatus having a gaseous fuel supply including a supply pipe, a burner and apilot light, an analyzer having a resistor responsive to the amount of flammable gases passed through the analyzer by the change of its resistance upon the lowering of its temperature by the presence of such flammable gases, a pipe connection for supplying said analyzer with a gas sample from the region near but spaced from the pilot light, a bridge circuit wherein said resistor is connected in one of the legs of the bridge circuit, a shut-oil. valve in the supply pipe of the fuel supply, a contact device electrically connected to said bridge circuit and actuated to its closed position when the presence of the flammable gases .in said analyzer approaches a dangerous condition, and electromagnetic means affected by the closing of said contact device for closing said valve.

3. The combination of combustion apparatus having a gaseous fuel supply including a supply pipe and a recirculating system of the burnt gases, an analyzer having a resistor responsive to the amount of flammable gases present in the composition of the gases passed through the analyzer by the change of its resistance upon the lowering of its temperature by the presence of such flammable gases, a pipe connection from a portion of the recirculating system for supplying a gas sample therefrom to the analyzer, a bridge circuit wherein said resistor is connected in one of the legs of the bridge circuit, a shutoff valve in the supply pipe of the fuel supply, a contact device electrically connected to said bridge circuit 9 and actuated to its closed position when the presence of the flammable gases passed through the analyzer from a portion of the recirculating system approaches a dangerous condition, and electromagnetic means affected by the closing of said contact device for closing said valve.

4. The combination of combustion apparatus having a gaseous fuel supply including a supply pipe, 9. fuel burner, an analyzer having a resistor responsive to the amount of flammable gases passed through the analyzer by the change of its resistance upon the lowering of its temperature by the presence of such flammable gases, a pipe connection from said apparatus in the region of the burnt gases for supplying a gas sample therefrom to the analyzer, a bridge circuit wherein said resistor is connected in one of the legs of the bridge circuit, a shut-off valve in the supply pipe of the fuel supply, a contact device electrically connected to said bridge circuit and actuated to its closed position when the presence of the flammable gases in said burnt gases approaches a dangerous condition, and electromagnetic means affected by the closing of said contact device for closing said valve.

5. The combination of combustion apparatus having a gaseous fuel burner and a fuel supply pipe therefor, a power driven mixer for supplying combustible gases to the apparatus, an analyzer having a resistor responsive to the amount of flammable gases present in the composition of the gases passed through the analyzer by the change of its resistance upon the lowering of its temperature by the presence of such flammable gases, a pipe connection from one side of the analyzer to the suction intake of said mixer, a pipe connection from the other side of the analyzer to a region in the path of the gases, 9. bridge circuit wherein said resistor is connected in one of the legs of the bridge circuit, a shutoff valve in the supply pipe of the fuel supply, a contact device electrically connected to said bridge circuit and actuated to its closed position when the presence of the flammable gases passed through the analyzer approaches a dangerous condition, and electromagnetic means affected by the closing of said contact device for closing said valve.

6. The combination of combustion apparatus having a gaseous fuel burner and a fuel supply pipe therefor, a pilot light for the burner, an analyzer having a resistor responsive to the amount of flammable gases present in the composition of the gases passed through the analyzer by the change of its resistance upon the lowering of its temperature by the presence of such flammable gases, a pipe connection from one side of the analyzer to the region near but spaced from the pilot light, a pipe connection from the other side of the analyzer to a region in the path of the burnt gases, a bridge circuit wherein said resistor is connected in one of the legs of the bridge circuit, a shut-oil? valve in the supply pipe of the fuel supply to the apparatus, a contact device electrically connected to said bridge circuit and actuated to its closed position when the presence of the flammable gases passes through said analyzer approaches a dangerous condition, and electromagnetic means affected by the closing of said contact device for closing said valve.

7. The combination of combustion apparatus having a gaseous fuel supply including a supply pipe, conduit means for withdrawing gases from said apparatus, an analyzer in said conduit means having a resistor responsive to the amount of flammable gases present in the composition of the gases withdrawn from the apparatus by the change of its resistance upon the lowering of its temperature by the presence of such flammable gases, a bridge circuit wherein said resistor is connected in one of the legs of the bridge circuit, a shut-oft valve in the supply pipe of the fuel supply. a signal, a contact device electrically connected to said bridge circuit and actuated to its closed position when the presence of the flammable gases in said apparatus approaches a dangerous condition, and electromagnetic means affected by the closing of said contact device for closing said valve and for operating said signal.

WALTER J. WIILENBORG.

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